Water resources affected by potentially toxic elements in an area under current and historical mining in northwestern Mexico

Overview of the heavy metal contamination in Mexico: sources of the contamination and issues in human health

This paper discusses information collected from original articles published between 1992 and 2022 regarding heavy metals (HMs) contamination in various environments across Mexico. The primary aim of this work was to identify the Mexican states where concentrations of HMs have been reported to exceed the maximum permissible limits for several types of soil, water, and sediment according to Mexican standards NOM-147-SEMARNAT/SSA1-2004, NOM-127-SSA1-2021, as well as international standards. The data collected indicates that 25 states in Mexico have reported at least one metal exceeding the maximum permissible limits in soil. Among these, Zacatecas, Nuevo Leon and Chihuahua had the highest number of HMs exceeding the standards. For sediment contamination, 26 states exceeded the permissible limits, with San Luis Potosí and Guerrero showing the highest number of HMs above the standards. Additionally, 26 states have reports of HMs exceeding the permissible limits in water, with Guanajuato and Guerrero having the highest number of HMs. Interestingly, the most frequent metals reported as soil contaminants are Cu, Fe, Pb and Zn; in sediment, they are Cd, Cr, Cu, Fe, Pb and Zn; and in water, they are Cd, Cr, Cu, Fe, Mn, Pb and Zn. The compiled information indicates that the primary anthropogenic sources of HMs release in Mexico include industrial activities, urban wastewater, mining, and agricultural practices. Furthermore, the data analyzed highlights several serious health risks associated with exposure to HMs, including cancer, central nervous system damage, DNA damage, and issues related to kidneys and lungs. This paper provides a comprehensive overview of HMs contamination in Mexico as well as the health challenges that arise from this contamination..

Ecological and human health risk assessment of potentially toxic elements in stagnant rainwater in Northwestern México

Urban stormwater management failures lead to floodingg. Potentially toxic elements (PTE) are commonly found in floods exposing population and ecosystems. Flooding is a persistent problem in the city of Hermosillo, Sonora thus PTE concentrations were determined, including threats to receiving ecosystems and population. The PTE concentrations were determined by MP-AES and compared to national and international guidelines. The non-carcinogenic and carcinogenic health risks were evaluated for adults and children following the EPA protocols. Al, Fe and Zn showed the highest concentrations. The concentrations exceeded consulted guideline criteria. PTE groups were identified relating to their sources and origin: (1) Fe, Mn, Ti and Al, (2) Cu, Cd and Cr, (3) Pb, Ni and Zn. Non-carcinogenic health effects and cancer risk were observed in the analyzed floodwater indicating that management measures should be taken to protect the flood-affected population.

Traceability and dispersion of highly toxic soluble phases from historical mine tailings: insights from Pb isotope systematics

Dispersion of potentially toxic elements associated with efflorescent crusts and mine tailings materials from historical mine sites threaten the environment and human health. Limited research has been done on traceability from historical mining sites in arid and semi-arid regions. Pb isotope systematics was applied to decipher the importance of identifying the mixing of lead sources involved in forming efflorescent salts and the repercussions on traceability. This research assessed mine waste (sulfide-rich and oxide-rich tailings material and efflorescent salts) and street dust from surrounding settlements at a historical mining site in northwestern Mexico, focusing on Pb isotope composition. The isotope data of tailings materials defined a trending line (R2 = 0.9); the sulfide-rich tailings materials and respective efflorescent salts yielded less radiogenic Pb composition, whereas the oxide-rich tailings and respective efflorescent salts yielded relatively more radiogenic compositions, similar to the geogenic component. The isotope composition of street dust suggests the dispersion of tailings materials into the surroundings. This investigation found that the variability of Pb isotope composition in tailings materials because of the geochemical heterogeneity, ranging from less radiogenic to more radiogenic, can add complexity during environmental assessments because the composition of oxidized materials and efflorescent salts can mask the geogenic component, potentially underestimating the influence on the environmental media.

Potentially toxic elements in soil-plant-water-animal continuum in a mining area from Northwestern Mexico: animal exposure pathways and health risks for children

Mining increases environmental concentrations of potentially toxic elements (PTEs) accumulating in organisms and spreading in the human food chain-their presence in milk is of great human health concern. Pathways were identified by which these elements reach raw milk from farms within a mining area in Northwestern Mexico; health risks for dairy cattle and children were also evaluated. Water from river and cattle waterers, as well as, soils showed that PTE concentrations generally below the Mexican and international limits; cattle forage concentrations were above the World Health Organization limits. Al, Mg, Mo, Ni and Zn were recorded in raw milk samples from the mining area, showing that Cd, Co, Cr, Cu, Pb and V are transferred from soil to plants but not accumulated in raw milk. Zn concentrations in raw milk exceeded the permissible limit; milk from farms without mining operations (comparison site) showed the presence of Al, Cr and Cu. In cattle tail hair, PTE did not correlate with raw milk concentrations. Metal accumulation in milk was higher through water consumption than that accumulated through forage consumption. Daily intakes (DI) of Al, Mg and Zn in cows could represent a risk for their health. The observed biotransference was higher than in other parts of Mexico, and the calculated DI and hazard quotients indicate no adverse health effects for children. However, the hazard Index values indicate that exposure to multiple PTE represents a risk for children. Management measures should be performed to control the cumulative risks to protect young children's health.